1. A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much calcium is contained in 40.0 g of calcium fluoride? 2. Silver has two isotopes. One isotope contains 60 neutrons and has a percent abundance of other contains 62 neutrons. Give the atomic symbols for the two isotopes. What is the average atomic weight of silver? 51.839% the 3. What is the mass (in grams) of a single chlorine molecule? 4. How many moles of ethanol (CH,CH-OH) are in 141 mg?